Superconductor circuit assembly



SUPERCONDUCTOR CIRCUIT ASSEMBLY Filed Feb. 15, 1965 United States PatentO Germany Filed Feb. 15, 1963, Ser. No. 258,799

Feb. 16, 1962,

Claims priority, application Germany,

7 claims. (ci. 307-885) My invention relates to electric circuits forcryogenic superconductors, for example magnets with excitation coilsconsisting of superconductors, or transformers with windings consistingof superconductors.

Such superconducting circuit components must be connected with circuitportions of the ordinary conductance type. A very high temperature dropoccurs at the connecting points due to the necessity of maintainingsuperconductors at extremely low temperatures. For example, thesuperconductors may be loc-ated within a gas-tight thermally insulatingenvelope lled with evaporating, liquid helium or other cryogenic agent,and copper conductorsy of conventional type pass through the gas-tightinsulating envelope. The copper conductor may be approximately ambientroom temperature. Hence, yan extreme temperature diiierence prevails atthe junction points between the superconductor and the ordinaryconductors and causes a correspondingly large amount of heat to flowfrom the copper Conductors to the superconductor.' This amount of heatmust be removed by means of the cooling agent. Due to the large coppercross sections in utility or industrial power plants the amount of heatthus to be removed by the cooling agent is so large as to greatlyincrease the consumption of cooling agent. This is undesirable becauseof the resulting increase in size of the low-temperature equipment aswell as for reasons of economy.

It is an object of my invention to overcome mentioned shortcomings.

According to a feature of my invention, I insert at the connecting pointof the superconductor with the ordinary conductor, thermoelectricallyeffective semiconductors in s-uch a manner as to block the flow of heatfrom the ordinary conductor to the superconductor, and preferably tocool the conductor.

According to another feature I insert such thermoelectric semiconductorsat both the respective connecting points of the superconductor with theordinary conductor.

According to still another feature I insert at the connecting point ofthe superconductor with the ordinary conductor two parallel electricpaths, and I include in each path a thermoelectric semiconductor and asemiconductor diode, the respective thermoelectric semiconductors beingof opposite conductivity and the respective diodes being oppositelypoled.

Other objects and advantages will be pointed out or become obvious fromthe following description of several embodiments of the presentinvention, reference being had to the accompanying drawings, in which:

FIG. 1 is a partially sectional view of a direct-current circuitIassembly embodying features of the invention;

FIG. 2 is a partially sectional view of part of an alternating currentassembly embodying features of the invention; and

FIG. 3 is a partially sectional view of another embodiment of the deviceillustrated in FIG. l.

the abovev this type are,

Patented July 12, 1966 ice In FiG. l, the circuit sections 1 and 2, eachcomprising `a copper conductor, are to be conductively connected bymeans of another circuit section comprising a superconductor 3.

This superconductor 3, excitation coil of a magnet tin (Nb3Sn),niobium-zirconium liurn or vanadium-silicon compounds. Thesuperconductor 3 is hermetically sealed within a thermal insulationvessel 4 which contains, for example, boiling helium 5 as a coolingagent. The above-mentioned copper leads 1 and 2 are inserted in agas-tight manner into the two end faces of the thermal insulation body4. Two thermoelectric semiconductors members 6 'and 7, each of which isinserted and embedded into the thermal insulation body, establishrespective connections between the copper leads 1 and 2 and thesuperconductor 3. Substances which are adapted for use asthermoelectrical semiconductors of for instance,bismuth-antimony-telluride (BiSbTeB), bismuth telluride (BigTes),bismuth selenide (BizSeg), bismuth-selenium-telluride, lead selenide,lead telluride, and bismuth antimonide. The compound bismuth antimonideconsists of 88% by weight of bismuth and 12% by weight of antimony and,depending on the operational temperature, can be located in a magneticfield of several hundred up to several thousand gauss.

With direct current device in the direction indicated by the arrow, ann-type thermoelectric semiconductor is provided at the current entrancepoint, whereas a p-type thermoelectric semiconductor is provided at thecurrent exit. For this pur- -pose the thermoelectric semiconductors areselected so that they will reduce or substantially lprevent heatconduction from the copper conductor to the superconductor. If desired,the semiconductor members may provide cooling, by the Peltier effect, onthe side of the copper conductor facing the superconductor.

The invention also contemplates that the transition from the temperatureof the boiling liquid coolant 5 to the ambient temperature of the copperleads be effected in several steps. For such purposes a plurality ofserially connected thermoelectrical semiconductors may be insertedbetween the two circuit portions 1 and 3, 2 and 3. The intermediatesteps are each adapted to be individually cooled. Substances which `areparticularly well suited for such cooling are evaporating hydrogen,evaporating air, ev-aporating carbon dioxide, evaporating ethylene,evapofor example, constitutes the and may be made of niobium- (NbZr),vanadium-galrating xenon, or evaporating ammonia. This secures par-lticularly good thermal blocking action between the superconductor andthe ordinary conductors of copper or other metals.

The above-described circuit assembly is not suited for superconductoroperation with alternating current, because it can prevent flow of heatonly for one direction of current flow. However, my invention alsoprovides for protection of the superconductor against the admission ofheat for both directions of current ow, as required inalternating-current operation. interpose between the superconductor andthe ordinary conductor a semiconductor device, as illustrated in FIG. 2in which identical elements `are denoted by the same reference numeralsas in FIG. 1.

According to FIG. 2, which shows only part of the device and only oneterminal thereof, this device com- I flowing through the conductor` Forthis purpose, 1

prises one superconductor 3 which constitutes the winding of atransformer, the thermal insulation 4, the cooling agent 5, and one ofthe copper conductors 2. Two respectively different parallel pathswithin the thermal insulation body 4 electrically connect thesuperconductor 3 and the copper conductor 2. The rst parallel pathconsists of an n-type thermoelectric semiconductor body 8, With asemiconductor diode arranged in series therepath is composed of a p-typethermoelectric seimconductor body 9, with a semiconductor diode 11 inseries therewith. Preferably crystaltype semiconductors of high loadcapacity, such as germanium or silicon, are used as semiconductordiodes. Both semiconductor diodes are of the n-p type, having layersarranged to form with the respective thermoelectric semiconductorbodies, an n-p-n layer structure in the rst path, and a p-n-p layerstructure in the second path. Thus, current flows readily in onedirection in the current path comprising the thermoelectricsemiconductor body 8 and the semiconductor diode 10. Current iiowsreadily in the other direction in the path comprising the thermoelectricsemiconductor body 9 and the semiconductor diode 11.

Instead of connecting such a thermoelectric semiconductor body in serieswith a semiconductor diode, it is also contemplated that athermoelectric semiconductor exerting a rectifying effect be used. Sucha rectifying device need be rated merely to block the voltage drop inthe diode and in the thermoelectric semiconductor body of the otherparallel path. Only very low reverse voltages with small voltage dropsare involved.

The feature mentioned with respect to FIG. l, wherein the transitionfrom the temperature of the boiling liquid to the ambient temperature ofthe copper leads is effected in several steps by series connected heatblocking means with each of the blocking means being cooled separatelyis also applicable to FIG. 2.

An embodiment of such a series assembly for direct current is shown inFIG. 3, wherein elements corresponding to the elements of FIG. l havebeen designated with like reference numerals. The transition from thetemperature of the liquid cooling agent 5 to the ambient temperature ofthe copper conductor 2 occurs in three steps through an inner,intermediate and outer cooling Wall, designated 4, 17 and 19respectively. The walls 4, 17 and 19 enclose spaces 5, 16 and 18respectively.

Where the current passes through the outer wall 19 of the thermallyinsulating vessel, the copper conductor 2 connects to an n-typethermoelectric semiconductor body 15. Within the intermediate space 18which contains liquid ethylene or xenon, and which is located betweenthe thermally insulating walls 17 and 19, the current is conducted by acopper or aluminum conductor 14. Current flows through the wall 17 via athermoelectric semiconductor body 13 exhibiting the Peltier effect, andthrough a copper or aluminum conductor 12 passing through the space 16which is filled with liquid nitrogen. The remaining construction withinthe wall 17 of the vessel corresponds to the structure illustrated inFIG. 1.

The thermoelectric semiconductor bodies 7, 13 and 15 each block heatiiow from the conductors 3, 12 and 14 in the respective chambers 5, 16and 18 to the respective adjacent conductors 12, 14 and 2.

While various embodiments of the invention have been described in detailit will be obvious to those skilled in the art that the invention may bepracticed otherwise.

I claim:

1. An electric superconductor circuit assembly, comprising a cryogenicsuperconductor and ordinary conductance-type conductor meanselectrically joined with each other, and two circuit branches eachinterposed between said superconductor and conductor means at thejunction location thereof and electrically joined with both in mutuallyparallel relation, said circuit branches each including thermoelectricsemiconductor means of respectively opposite conductance types andsemiconductor opposite polarity for reducing heat supply from saidconductor means to said superconductor when traversed by electriccurrent.

2. An electric superconductor circuit assembly, comprising a cryogenicsuperconductor and ordinary conductance-type conductor meanselectrically joined With each other, and two circuit branches eachinterposed between said superconductor and conductor means at the thejunction location thereof and electrically joined with both in mutuallyparallel relation, and diodes of opposite polarity in series with therespective thermoelectric semiconductor means for reducing heat supplyfrom said conductor means to said superconductor when traversed byelectric current.

3. An electric superconductor circuit assembly, comprising asuperconductor having cryogenic cooling means, two conductors ofordinary conductance type between which said superconductor is connectedelectrically in series, two joining means each interposed between andconductively joined with said superconductor and said two otherconductors respectively, said joining means each comprising a pair ofcircuit branches each joining said superconductor and said conductors,said circuit branches of each pair each including one of twothermoelectric semiconductor means of respectively opposite conductancetypes and one of two semiconductor diodes of respectively oppositepolarity in series with the respective thermoelectric semiconductormeans for reducing heat supply from said conductor means to saidsuperconductor when traversed by electric current.

4. An electric superconductor circuit assembly, comprising a cryogenicsuperconductor and ordinary conductance-type conductor meanselectrically joined with each other, and a pair of circuit branches eachinterposed between said superconductor and conductor means at thejunction location thereof and electrically joined with both in mutuallyparallel relation, said branches each including thermoelectricsemiconductor means and diodes in series with the respectivethermoelectric semiconductor means for reducing heat supply from saidconductor means to said superconductor when traversed by electriccurrent, said semiconductor means and said diodes of the two circuitbranches having respective conductance types and polarities arrangedrespectively in p-n-p and n-p-n relation.

5. An electric superconductor circuit assembly, prising a cryogenicsuperconductor and ordinary conductance-type conductor meanselectrically joined with each other, and two circuit paths eachinterposed between said superconductor and conductor means at thejunction location thereof and electrically joined with both in mutuallyparallel relation, said circuit paths each including a thermoelectricsemiconductor means of respectively opposite conductance types forreducing heat supply from said conductor means to said superconductorWhen traversed by electric current, said semiconductor means havingrectifying properties for exerting a rectifying effect.

6. An electric superconductor circuit assembly comprising a cryogenicsuperconductor, a plurality of ordinary conductance type conductor meanselectrically joined in series with each other and with saidsuperconductor, a plurality of thermoelectric semiconductor members eachinterposed at the respective junction locations, and electrically joinedwith the adjacent conductor means and superconductor forthermoelectrically reducing the heat supply between said conductor meansand said superconductor when traversed by electric current and separatecooling means for said plurality of conductor means and saidsuperconductor.

7. An electric superconductor circuit assembly comprising a cryogenicsuperconductor, a plurality of ordinary conductance type conductor meanselectrically joined in series with each other and with saidsuperconductor, and a plurality of joining means each interposed atrespective junction locations and electrically joined with Comsaidsuperconductor and said respective conductor means, said joining meanseach comprising two circuit branches each joining said superconductorand said conductor means, said circuit branches each including one oftwo thermoelectric semiconductor means of respectively oppositeconductance types and one of two semiconductor diodes of respectivelyopposite polarity in series with the respective thermoelectricsemiconductor means and sepa rate cooling means for said yconductormeans and said superconductor.

UNITED STATES PATENTS 12/ 1960 Seegert 62-3 X 4/ 1961 Hanlein 62-3ARTHUR GAUSS, Primary Examiner. JOHN W. HUCKERT, Examiner. 10 M. LEE, R.H. EPSTEIN, Assistant Examiners.

1. AN ELECTRICAL SUPERCONDUCTOR CIRCUIT ASSEMBLY, COMPRISING A CRYOGENIC SUPERCONDUCTOR AND ORDINARY CONDUCTANCE-TYPE CONDUCTOR MEANS ELECTRICALLY JOINED WITH EACH OTHER, AND TWO CIRCUIT BRANCHES EACH INTERPOSED BETWEEN SAID SUPERCONDUTOR AND CONDUCTOR MEANS AT THE JUNCTION LOCATION THEREOF AND ELECTRICALLY JOINED WITH BOTH IN MUTUALLY PARALLEL RELATION, SAID CIRCUIT BRANCHES EACH INCLUDING THERMOELECTRIC SEMICONDUCTOR MEANS OF RESPECTIVELY OPPOSITE CONDUCTANCE TYPES AND SEMICONDUCTOR DIODES OF RESPECTIVELY OPPOSITE POLARITY FOR REDUCING HEAT SUPPLY FROM SAID CONDUCTOR MEANS TO SAID SUPERCONDUCTOR WHEN TRAVERSED BY ELECTRIC CURRENT. 